Although the causes of cancer ____we do not yet have any practical way to prevent it.
| A．are being uncovered | B．have been uncovering |
| C．are uncovering | D．have uncovered |
________ one of you breaks the window will have to pay for it.
| A．Whoever |
| B．Whatever |
| C．Whichever |
| D．Wherever |
________ makes the book so extraordinary is the creative imagination of the writer.
| A．That |
| B．What |
| C．Who |
| D．Which |
No one ________ the building without the permission of the policeman.
| A．is leaving |
| B．is to leave |
| C．has left |
| D．will be leaving |
We usually take turns ________ some cleaning, and today it is my turn ________ it.
| A．to do; doing |
| B．do; do |
| C．done; doing |
| D．to do; to do |
Seeing the bad results of the exams, she was rather frustrated and felt _________ about her future.
| A．surprising |
| B．puzzling |
| C．puzzled |
| D．surprised |